Assessing the implications of the loss of set‐aside for farmland birds

Between 1988 and 2007, set‐aside, a European Commission production control measure, took an average of 10% of arable farmland in the EU out of production each year. In 2007, the set‐aside rate was set to 0% and the scheme was later abandoned altogether. By assessing associations of farmland birds with set‐aside and quantifying the extent of set‐aside loss, this study aims to assess the implications of set‐aside loss for farmland bird conservation. During the lifespan of set‐aside, a large number of studies assessed the biodiversity value of set‐aside and other agricultural crops and habitats. Where possible we considered measurable benefits of set‐aside. However, some studies did not specify the type of set‐aside and in some cases set‐aside fields were grouped with cereal stubble fields. In these cases, we took the pragmatic approach of assessing the value of generic stubble fields as a conservative minimum estimate of the value of set‐aside fields. A re‐analysis of data from 30 intensive studies demonstrates that farmland bird densities tended to be higher on set‐aside than on either cereal or oilseed rape crops. Without mitigation, these are the two crops likely to replace most set‐aside fields. We estimate that 26–52% of the farmland populations of key granivorous passerines were present on stubble fields, giving an indication of the proportion of birds likely to be present on set‐aside fields within this broader category. An extensive survey of lowland farmland during winters 1999/2000, 2000/2001 and 2002/2003, repeated in February 2008, showed a doubling of the number of 1‐km squares with no stubble and a halving of the number of squares with more than 10 ha of stubble. After set‐aside abandonment, 72% of squares had no stubble in the important late winter period, confirming that many of the former stubble fields were retained as set‐aside. A simple correlative model suggests that this could cause a small increase in the rate of decline of Skylark Alauda arvensis and Yellowhammer Emberiza citrinella populations, assuming causal links between stubble area and demography. However, even if this assumption cannot be supported, these results clearly indicate that a significant proportion of some farmland bird populations will need to find alternative breeding and foraging habitats.     

Intra‐specific variance in sperm morphometry: a comparison between wild and domesticated Zebra Finches Taeniopygia guttata

The Zebra Finch Taeniopygia guttata is a model bird species for the experimental study of behavioural and evolutionary concepts in captivity and especially sexual selection. The validity of sexual selection studies of domesticated birds is of long‐standing concern as little is known about the influence of domestication on sexually selected traits. Most domesticated Zebra Finch populations are maintained under a strict breeding regime to avoid potential inbreeding. However, these breeding regimes may interfere with the processes of sexual selection and influence the evolution of sexually selected traits because they may limit or prohibit active mate choice. Here, we investigated the potential impact of a monogamous breeding scheme in a domesticated population in which active mate choice is largely inhibited, on the evolution of sperm morphometry as a sexually selected trait. We compared sperm morphometric traits (total sperm length and length of sperm head, midpiece and flagellum), and the variance thereof, between a domesticated and two wild Zebra Finch populations. Although we found significant differences between the three populations for certain sperm traits (head length, midpiece length), which may be of importance in postcopulatory sexual selection, overall, variance in sperm morphometry did not differ between the domesticated and the wild Zebra Finch populations. Our results validate the use of domesticated Zebra Finches for further studies of postcopulatory sexual selection and sperm competition.     

Can macroinvertebrate rapid bioassessment methods be used to assess river health during drought in south eastern Australian streams?

• 1 Despite significant concern about drought impacts in Australia, there have been no broad‐scale studies of drought effects on river health. A severe and prolonged drought has been acting on many streams in south eastern Australia over the past decade. EPA Victoria has undertaken rapid bioassessment (RBA) of over 250 stream reference sites since 1990, providing an opportunity for a before‐after‐control‐impact investigation of drought related changes to macroinvertebrate indices and water quality. This study uses data from 1990 to 2004 to critically evaluate the effectiveness of using RBA methods and indices, which were designed for assessment of human impacts, for monitoring streams during drought.
• 2 Reference stream sites across Victoria (those with minimal anthropogenic disturbances and repeatedly sampled) were classified as being ‘in drought’ or ‘not in drought’ using the Bureau of Meteorology’s rainfall deficiency definition. Four biological indices (SIGNAL, EPT, Family Richness and AUSRIVAS) were calculated for combined autumn and spring samples for edge and riffle habitats for the selected sites.
• 3 General linear models and paired t‐tests were used to detect drought related changes to index and water quality values at state‐wide and bioregional scales. Changes in taxa constancy were examined to determine which taxa were sensitive to or benefited from drought conditions. Frequency of site failure against biological objectives specified in the State Environment Protection Policy (Waters of Victoria) (herein termed ‘SEPP WoV’) before and during drought was also examined to detect changes in a management context.
• 4 Few significant changes in index values were detected for riffle habitat samples. Rates of failure against biological objectives were similar before and during drought for riffle samples. In contrast, edge habitat AUSRIVAS and SIGNAL scores were significantly reduced at the state‐wide scale and most indices showed significant declines in the lower altitude forests, and foothills and coastal plains bioregions.
• 5 Generally, more pollution tolerant, lentic taxa replaced sensitive and flow‐requiring taxa in edge samples during drought. In contrast, there were few reductions in the taxa of riffle samples during drought. However, many pool preferring, but pollution sensitive taxa occurred more frequently in riffle areas. Hence, the riffle community began to resemble that of pools and edges. This was attributed to decreased flow and increased ‘lentic’ habitat opportunities in riffles.
• 6 Detection of a drought effect was confined to the edge habitat and site failure could be assigned to drought and anthropogenic impacts, in conjunction or alone. The riffle sampling protocol was resistant to detection of drought effects as samples were only taken when sufficient water was present within this habitat. Therefore, biological changes at sites not meeting policy objectives for riffle habitats can be attributed to anthropogenic rather than drought impacts.

     

Global assessment of coral bleaching and required rates of adaptation under climate change

Elevated ocean temperatures can cause coral bleaching, the loss of colour from reef‐building corals because of a breakdown of the symbiosis with the dinoflagellate Symbiodinium. Recent studies have warned that global climate change could increase the frequency of coral bleaching and threaten the long‐term viability of coral reefs. These assertions are based on projecting the coarse output from atmosphere–ocean general circulation models (GCMs) to the local conditions around representative coral reefs. Here, we conduct the first comprehensive global assessment of coral bleaching under climate change by adapting the NOAA Coral Reef Watch bleaching prediction method to the output of a low‐ and high‐climate sensitivity GCM. First, we develop and test algorithms for predicting mass coral bleaching with GCM‐resolution sea surface temperatures for thousands of coral reefs, using a global coral reef map and 1985–2002 bleaching prediction data. We then use the algorithms to determine the frequency of coral bleaching and required thermal adaptation by corals and their endosymbionts under two different emissions scenarios. The results indicate that bleaching could become an annual or biannual event for the vast majority of the world's coral reefs in the next 30–50 years without an increase in thermal tolerance of 0.2–1.0°C per decade. The geographic variability in required thermal adaptation found in each model and emissions scenario suggests that coral reefs in some regions, like Micronesia and western Polynesia, may be particularly vulnerable to climate change. Advances in modelling and monitoring will refine the forecast for individual reefs, but this assessment concludes that the global prognosis is unlikely to change without an accelerated effort to stabilize atmospheric greenhouse gas concentrations.     

Drought and Oxidative Load in the Leaves of C3 Plants: a Predominant Role for Photorespiration?

Although active oxygen species are produced at high rates inboth the chloroplasts and peroxisomes of the leaves of C₃ plants,most attention has focused on the potentially damaging consequencesof enhanced chloroplastic production in stress conditions suchas drought. This article attempts to provide quantitative estimatesof the relative contributions of the chloroplast electron transportchain and the glycolate oxidase reaction to the oxidative loadplaced on the photosynthetic leaf cell. Rates of photorespiratoryH₂O₂ production were obtained from photosynthetic and photorespiratoryflux rates, derived from steady-state leaf gas exchange measurementsat varying irradiance and ambient CO₂. Assuming a 10 % allocationof photosynthetic electron flow to the Mehler reaction, photorespiratoryH₂O₂ production would account for about 70 % of total H₂O₂ formedat all irradiances measured. When chloroplastic CO₂ concentrationrates are decreased, photorespiration becomes even more predominantin H₂O₂ generation. At the increased flux through photorespirationobserved at lower ambient CO₂, the Mehler reaction would haveto account for more than 35 % of the total photosynthetic electronflow in order to match the rate of peroxisomal H₂O₂ production.The potential signalling role of H₂O₂ produced in the peroxisomesis emphasized, and it is demonstrated that photorespiratoryH₂O₂ can perturb the redox states of leaf antioxidant pools.We discuss the interactions between oxidants, antioxidants andredox changes leading to modified gene expression, particularlyin relation to drought, and call attention to the potentialsignificance of photorespiratory H₂O₂ in signalling and acclimation.